[postgis-users] Data Versioning?

[Jeff McKenna]

I guess I was hoping to hear that PostGIS/PostgreSQL already handled 
spatial data versioning similar to ArcSDE.
I understand the concept of 'meta tables' storing extra timestamp info, 
but are there examples of this already in use out there?  Has anyone 
been successful in implementing spatial data versioning with 
PostGIS/PostgreSQL????  (we deal with large datasets and this would 
impact the way we do things bigtime)

thanks.


Jeff





Obe, Regina DND\\MIS wrote:
> I'm not familiar with how SDE does it - but it would seem to me to implement
> such a thing in PostGIS/PostGresql - that as you said you would have a meta
> table of some sort which maybe mirrors the original table but has extra
> fields to keep track of whether it is a delete/insert/update and the
> datetime stamp.  The only reason I wouldn't keep it in the same table is
> that to the unsuspecting user who just wants the latest version (and doesn't
> ahve aneed to revert etc.) -  it's unnecessary processing to weed out older
> versions.
> 
> I would do this versioning in the database though with a before trigger on
> the spatial table that on insert/update/or delete copies the prior version
> of the record into the meta table.
> 
> 
> 
> -----Original Message-----
> From: Gary Sherman [mailto:sherman at mrcc.com]
> Sent: Wednesday, July 09, 2003 10:11 PM
> To: 'PostGIS Users Discussion'
> Subject: RE: [postgis-users] Data Versioning?
> 
> 
> ArcSDE implements versioning at the server (read SDE software)  level.
> The database tier has no inherent "versioning" capability, regardless of
> whether it is running on Oracle, Informix or Brand X. Versioning is
> implemented using "delta" tables that track changes (adds and deletes)
> across versions. There are a slew of other tables (what I call "meta"
> tables) that make up the ArcSDE schema.
> 
> My guess is that a middle tier would be required between
> PostgreSQL/PostGIS and the client to implement a versioning scheme
> similar to ArcSDE.
> 
> -gary
> 
> -----Original Message-----
> Subject: Re: [postgis-users] Data Versioning?
> 
> 
> SDE is ESRIs Spatial Database Engine.  It supports versioning for
> GeoSpatial data the same way that CVS does this for code.  CVS will not
> work for this purpose, as Spatial Data stored in PostGIS is not stored
> in flat text files like source code.  Postgres / PostGIS would need to
> support this directly.
> 
> I don't have the answer to the question, but am also very interested to
> know if Postgres/PostGIS support any form of geospatial data versioning.
> I am also curious to know if it supports long transactions.  I should
> probably RTFM before asking though.
> 
> --Craig
> 
> 
> 
> ----- Original Message ----- 
> From: "Rich Shepard" <rshepard at appl-ecosys.com>
> To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
> Sent: July 09, 2003 3:36 PM
> Subject: Re: [postgis-users] Data Versioning?
> 
> 
> 
>>On Wed, 9 Jul 2003, Jeff McKenna wrote:
>>
>>
>>>Pardon my beginner question, but I am trying to find out how 
>>>PostGIS/PostgreSQL handles data versioning.  Myself I am familiar 
>>>with SDE, but would love to find an open source alternative to 
>>>versioning
>>
> large
> 
>>>datasets.  Does PostGIS handle data versioning?  If not, are there 
>>>plans for this in the future?  Are there any documents/past email 
>>>postings regarding this?  Thanks.
>>
>>Jeff,
>>
>>  I've no idea what SDE might be, but there's always CVS. This is used
> 
> 
>>primarily for source code development projects, but I've used it for 
>>document development, too. So, I imagine that one could check in and 
>>out different data sets, too.
>>
>>Rich
>>
>>Dr. Richard B. Shepard, President
>>
>>                       Applied Ecosystem Services, Inc. (TM)
> 
> 
> 
> 



-- 
Jeff McKenna
GIS Specialist
DM Solutions Group Inc.
http://www.dmsolutions.ca